/*
 * Copyright (c) 2018, SnakeYAML
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */
package org.snakeyaml.engine.v2.events;

import java.util.Objects;
import java.util.Optional;
import org.snakeyaml.engine.v2.common.Anchor;
import org.snakeyaml.engine.v2.exceptions.Mark;

/** Base class for all events that mark the beginning of a node. */
public abstract class NodeEvent extends Event {

  private final Optional<Anchor> anchor;

  public NodeEvent(Optional<Anchor> anchor, Optional<Mark> startMark, Optional<Mark> endMark) {
    super(startMark, endMark);
    Objects.requireNonNull(anchor);
    this.anchor = anchor;
  }

  /**
   * Node anchor by which this node might later be referenced by a {@link AliasEvent}.
   *
   * <p>Note that {@link AliasEvent}s are by it self <code>NodeEvent</code>s and use this property
   * to indicate the referenced anchor.
   *
   * @return Anchor of this node or <code>null</code> if no anchor is defined.
   */
  public Optional<Anchor> getAnchor() {
    return this.anchor;
  }
}
